Help understing locking tokens

Hi, I have just deployed a token for a project and it currently says I have 40% of the total supply after i burned the 60%. I need to to hold 5% of the total supply for marketing and lock the rest of the token.

should i use dexsale?
when do that do I add the liquidity first or after?
will people still be able to buy if I lock most of the token?

Could you please share your source code?